A compact disk (hereinafter, referred to as "CD") system, which has been standardized in the so-called "red book", the so-called "yellow book" or the like and in which information is recorded in a disk having a diameter of 120 mm, and which is used mainly for music information has been widely adopted. This system has an almost sufficient capacity for handling music information, but when recording video information as in a CD-ROM, its capacity becomes insufficient for an increased amount of information, thus resulting in insufficient recording time or degraded image quality. Attempts to deal with this problem includes, for example, a digital video disk (hereinafter referred to as "DVD") system and the like.
In the aforementioned CD system, the disk is mainly used on only one side or face for exclusive reproduction. Also, the disk is often handled in a bare state, and a tray loading system, in which the disk is mounted on a drawer-shaped tray coming out from a disk device, is mainly used because of its good operability. On the other hand, however, a disk cartridge, which is called a CD caddy, as described in Japanese Laid-Open Patent Application No. 63-153376 and in Japanese Laid-Open Patent Application No. 63-47472, capable of taking a disk out and in, is used, and a front loading system for inserting this disk cartridge into the device is also utilized.
In addition, in the aforementioned DVD system, the disk is used on both sides or faces for recording and/or reproduction. The disk tends to be housed in an exclusive cartridge primarily for protection from the standpoint of securing the reliability resulting from higher density recording.
Further, in contrast to the CD system, which is mainly used for exclusive reproduction, there has also been announced a PD (Phase-change Disk) system capable of rewriting, as described in Optical Disk System for Multimedia National Technical Report, Vol. 4, No. 6, December 1994, pgs. 129-136. In this PD system, the disk is used on one side for recording and/or reproduction. Also, the disk is housed in an exclusive cartridge from the standpoint of securing the reliability resulting from rewriting.
Disks for use with each system of the aforementioned CD, DVD and PD all have a diameter of 120 mm, and cartridges for each system described above are of nearly the same shape, having the same dimensions.
The problem to be solved by the present invention is to increase the capacity of the CD system or a disk system having nearly the same dimensions as the CD system, and the concept and technical problems for the disk cartridge and disk device using the same to deal with the problem are described below.
1) In order to take measures against scratching, dust and dirt resulting from higher density recording, a state in which a disk has been placed in a cartridge is supposed to be a standard. Even in the CD system, there is present a case called a "CD caddy" which is about 135 mm long, about 125 mm wide and about 8 mm thick, but this CD caddy is not used currently. Rather, the so-called tray loading system is mainly used.
2) Allowing both faces of the disk to be recorded. The CD is for one side recording and the capacity can be doubled by simple calculation.
3) Making a disk which is CD compatible and reproducible In a disk device using a new disk cartridge, its sales point is to make the existing CD compatible and reproducible. Accordingly, it is an indispensable condition to enable taking a disk in and out and having a disk for CD system within. However, the CD caddy is for one-side recording, and a clamper of the disk is attached on the side of the caddy case. The clamper is constructed to be on the side of the disk device because the new disk cartridge is of a both-face recording system. Thus, if the CD caddy is mounted to a disk device for the new disk cartridge, two clampers will interfere with each other. Therefore, it is necessary to prevent the CD caddy from being mounted to the disk device of the new disk cartridge.
4) Supply of the disk and disk cartridge at a low price. In order to reduce the price for general family usage, the disk cartridge including the disk device is required to be constructed at low cost.
Further, when increasing the capacity as described above, the mixed existence of three similar disk cartridges poses the following problems.
5) Discrimination of disk cartridges for each system
6) Prevention of erroneous insertion
7) The system of mounting the cartridge to the device is made applicable to both the front loading system and the tray loading system.